Try this demo:

use strict;
use warnings;

{
    my $str = "0123456789";
    for (1 .. 5) {
        chop $str;
    }
    print "[$str]";
}

{
    my $str = "0123456789";
    for (1 .. 5) {
        chomp $str;
    }
    print "[$str]";
}

{
    my $str = "0123456789\n";
    for (1 .. 5) {
        chop $str;
    }
    print "[$str]";
}

{
    my $str = "0123456789\n";
    for (1 .. 5) {
        chomp $str;
    }
    print "[$str]";
}
[download]

It prints (observe it):

[01234][0123456789][012345][0123456789]
[download]

And read perlfunc.