Taint won't let you feed data from a filehandle directly into an eval because that filehandle could feed you anything, including something terribly destructive. You have to read the file contents into a scalar and untaint it before it can be evaled, like so:

#!/usr/bin/perl -wT
use strict;

open (DATA, "<foo.txt") || die;
while (my $dataline = <DATA>) {
  $dataline =~ /(print '[^']*';)/ || next;
  eval $1;
  print "\n";
}
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