Tangential observation: Pro forma untainting may be worse than none:

#!/usr/bin/perl -T
use 5.016;

my $regex =  qr/^.*$/;     # match anything, including an empty string

my @strings = ('delete everything',
               'overclock till cpu smokes',
               'we ownz you exec(nasty code here)',
               ' ',
               '',
              );

untaint(@strings);

sub untaint() {
    
    for my $elem(@strings) {
        if ( $elem =~ /$regex/ ) {
            say "Thank you, sucker. You are borked, really bad!";
        }else{
            say "Oh look, untainting did something more than merely al
+low any-old-badstruff to pass untaint. string untainted was -|$elem|-
+";
        }
    }
}
[download]

Execution produces:

C:\>untaint-bad.pl
Thank you, sucker. You are borked, really bad!
         |delete everything|' passed.
Thank you, sucker. You are borked, really bad!
         |overclock till cpu smokes|' passed.
Thank you, sucker. You are borked, really bad!
         |we ownz you exec(nasty code here)|' passed.
Thank you, sucker. You are borked, really bad!
         | |' passed.
Thank you, sucker. You are borked, really bad!
         ||' passed.
[download]