use warnings;
use strict;

one();

exit(0);

sub one {
	my $str = 'hello, world!';
	two($str);
}
sub two {
	my $str = shift;
	$str =~ s/hello/goodbye/;
	three($str);
}
sub three {
	my $str = shift;
	print "$str\n";
}

##</code><code>##

goodbye, world!

##</code><code>##

perl -wMstrict -MDevel::Trace::Subs=install_trace -e 'install_trace(file => "trace.pl");'

##</code><code>##

use Devel::Trace::Subs qw(trace trace_dump); # injected by Devel::Trace::Subs
use warnings;
use strict;

one();

exit(0);

sub one {
    trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs

    my $str = 'hello, world!';
    two($str);
}
sub two {
    trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs

    my $str = shift;
    $str =~ s/hello/goodbye/;
    three($str);
}
sub three {
    trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs

    my $str = shift;
    print "$str\n";
}

##</code><code>##

$ENV{DTS_ENABLE} = 1; # add this line before the first sub call

trace_dump(); # add this line after the last sub call

##</code><code>##

goodbye, world!

Code flow:

    1: main::one
    2: main::two
    3: main::three

Stack trace:

    in:      main::one
    sub:     -
    file:    ./trace.pl
    line:    8
    package: main

    in:      main::two
    sub:     main::one
    file:    ./trace.pl
    line:    19
    package: main

    in:      main::three
    sub:     main::two
    file:    ./trace.pl
    line:    27
    package: main

##</code><code>##

perl -wMstrict -MDevel::Trace::Subs=remove_trace -e 'remove_trace(file => "trace.pl");'

##</code><code>##

sudo perl -MDevel::Trace::Subs=install_trace -e 'install_trace(file=>"Data::Dump");'

##</code><code>##

perl -MData::Dump -MDevel::Trace::Subs=trace_dump -e '$ENV{DTS_ENABLE}=1; dd {a => 1}; trace_dump'

{ a => 1 }

Code flow:

    1: Data::Dump::dd
    2: Data::Dump::dump
    3: Data::Dump::_dump
    4: Data::Dump::tied_str
    5: Data::Dump::_dump
    6: Data::Dump::format_list


Stack trace:

    in:      Data::Dump::dd
    sub:     -
    file:    -e
    line:    1
    package: main

    in:      Data::Dump::dump
    sub:     Data::Dump::dd
    file:    /usr/lib/perl5/site_perl/5.22.0/Data/Dump.pm
    line:    84
    package: Data::Dump

    in:      Data::Dump::_dump
    sub:     Data::Dump::dump
    file:    /usr/lib/perl5/site_perl/5.22.0/Data/Dump.pm
    line:    36
    package: Data::Dump

    in:      Data::Dump::tied_str
    sub:     Data::Dump::_dump
    file:    /usr/lib/perl5/site_perl/5.22.0/Data/Dump.pm
    line:    292
    package: Data::Dump

    in:      Data::Dump::_dump
    sub:     Data::Dump::_dump
    file:    /usr/lib/perl5/site_perl/5.22.0/Data/Dump.pm
    line:    331
    package: Data::Dump

    in:      Data::Dump::format_list
    sub:     Data::Dump::dump
    file:    /usr/lib/perl5/site_perl/5.22.0/Data/Dump.pm
    line:    65
    package: Data::Dump

##</code><code>##

sudo perl -MDevel::Trace::Subs=remove_trace -e 'remove_trace(file=>"Data::Dump");'