1Data::Dumper::Names(3)User Contributed Perl DocumentationData::Dumper::Names(3)
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NAME

6       Data::Dumper::Names - Dump variables with names (no source filter)
7

VERSION

9       Version 0.03
10

SYNOPSIS

12           use Data::Dumper::Names;
13
14           my $foo = 3;
15           my @bar = qw/this that/;
16           warn Dumper($foo, \@bar);
17           __END__
18           output:
19
20           $foo = 3;
21           @bar = (
22               'this',
23               'that'
24           );
25

EXPORT

27       Like Data::Dumper, this module automatically exports "Dumper()" unless
28       a null import list is explicitly stated.
29
30       This module should be considered ALPHA.
31

FUNCTIONS

33   Dumper
34        warn Dumper($foo, \@bar);
35
36       "Dumper" returns a string like "Dumper" but the variable names are
37       prefixed for you.  Unlike Data::Dumper::Simple, arrays and hashes must
38       be passed by reference.
39

CAVEATS

41   PadWalker
42       This module is an alternative to Data::Dumper::Simple.  Many people
43       like the aforementioned module but do not like the fact that it uses a
44       source filter.  In order to pull off the trick with this module, we use
45       PadWalker.  This introduces its own set of problems, not the least of
46       which is that PadWalker uses undocumented features of the Perl
47       internals and has an annoying tendency to break.  Thus, if this module
48       doesn't work on your machine you may have to go back to
49       Data::Dumper::Simple.
50
51   References
52       Arrays and hashes, unlike in Data::Dumper::Simple, must be passed by
53       reference.  Unfortunately, this causes a problem:
54
55        my $foo = \@array;
56        warn Dumper( $foo, \@array );
57
58       Because of how pads work, there is no easy way to disambiguate between
59       these two variables.  Thus, "Dumper" may identify them as $foo or it
60       may identify them as @array.  If it misidentifies them, it should at
61       least do so consistently for the individual call to "Dumper".  (For
62       Perl 5.8 and after, subsequent calls to "Dumper" may have different
63       results in the above case.  This is because of how Perl handles hash
64       ordering).
65
66   Call stack level
67       You generally will call things with this:
68
69        warn Dumper($foo, $bar, \@baz);
70
71       However, you might be refactoring code and want to shove that into a
72       subroutine somewhere.  In that case, you'll need to set (via "local"!),
73       the $Data::Dumper::Names::UpLevel variable.  It defaults to one, but
74       you might set it to a higher level, depending on how high up the call
75       stack those variables are really located:
76
77        sub show {
78            return unless $ENV{VERBOSE};
79            local $Data::Dumper::Names::UpLevel = 2;
80            warn Dumper(@_);
81        }
82
83       Note that if you fail to use "local", subsequent calls to "Dumper" may
84       be looking at the wrong call stack level.
85
86   Unknown Variables
87       The easiest way to have things "just work" is to make sure that you can
88       see the name of the variable in the "Dumper" call:
89
90        warn Dumper($foo, \@bar); # good
91        warn Dumper($_);          # probably will get output like $VAR1 = ...
92        warn Dumper($bar[2]);     # probably will get output like $VAR1 = ...
93
94       Usually the output from Dumper will be something like this:
95
96        $foo = 3;
97        @bar = (
98           'this',
99           'that'
100        );
101
102       However, sometimes a $VAR1 or $VAR2 will creep in there.  This happens
103       if pass in anything but a named variable.  For example:
104
105        warn Dumper( $bar[2] ); # $VAR1 = ... can't figure out the name
106
107       We probably won't be able to figure out the name of the variable
108       directly unless we took the time to walk all data structures in scope
109       at the time "Dumper" is called.  This is an expensive proposition, so
110       we don't do that.  It's possible we will be able to figure out that
111       name, but only if the variable was assigned its value from a reference
112       to a named variable.
113
114        $bar[2] = \%foo;
115        warn Dumper( $bar[2] );
116
117       "Dumper", in the above example, will identify that variable as being
118       %foo.  That could be confusing if those lines are far apart.
119
120        foreach ( @customer ) {
121           print Dumper( $_ );
122        }
123
124       It should go without saying that the above will also probably not be
125       able to name the variables.
126

AUTHOR

128       Curtis "Ovid" Poe, "<ovid@cpan.org>"
129

BUGS

131       Please report any bugs or feature requests to
132       "bug-data-dumper-names@rt.cpan.org", or through the web interface at
133       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Data-Dumper-Names>.  I
134       will be notified, and then you'll automatically be notified of progress
135       on your bug as I make changes.
136

ACKNOWLEDGEMENTS

138       See Data::Dumper and Data::Dumper::Simple.
139
140       Thanks to demerphq (Yves Orton) for finding a bug in how some variable
141       names are reported.  See Changes for details.
142

144       Copyright 2005 Curtis "Ovid" Poe, all rights reserved.
145
146       This program is free software; you can redistribute it and/or modify it
147       under the same terms as Perl itself.
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151perl v5.32.1                      2021-01-27            Data::Dumper::Names(3)
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