Are you familiar with regular expressions? If not, read through perlre and perlreftut. Using the substitution operator is a common way to remove strings. This should get you started:

use strict;
use warnings;

my $str = q{ZZ<<;ght;''d;\r\n\t\t\t\t\t;$_;LicBpack;'c*'y=eval;perl$@p
+op&&die@;D9};
$str =~ s/\by\b//g;
$str =~ s/\beval\b//g;
$str =~ s/\bdie\b//g;
$str =~ s/\\(n|r)//g;   # alternation
print $str, "\n";
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prints:

ZZ<<;ght;''d;\t\t\t\t\t;$_;LicBpack;'c*'=;perl$@pop&&@;D9
[download]

Give it a try. If you still can not solve your problem, post some code that you have tried, and ask detailed questions.