Hello honorable Monks, Today I uncovered a very subtle bug in one of my programs, and although I fixed it I have no idea what is actually going on. Here is an example program that demonstrates what happens:

#!/usr/bin/perl

my $test = 'abc , def';

for my $sub qw/trim_start trim_end trim_start trim_end/ {
    $test =~ /([\s\w]+),([\s\w]+)/;

    $sub->($1, $2);
}

sub trim_start {
    while (@_) {
        my $string = shift @_;
        $string =~ s/\A\s+//ms;

        print "$string\n";
    }
}

sub trim_end {
    while (@_) {
        my $string = shift @_;
        $string =~ s/\s+\z//ms;

        print "$string\n";
    }
}
[download]

What is the difference between the two regexes? Why does only trim_end() destroy $2? I solved my problem by doing:

my @args = @_;
while (@args)...
[download]

but I still would like to know what causes this.

Thank you in advance.

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