$input = '...'; # input from user
$value = '...'; # String I want to test to see if $input matches

# escape s/delimiter/
$input =~ s|/|\/|gs;

# strip new lines - not expected in input anyway 
$input =~ s/\n//gs;

my $match;
eval q{
  $value =~ /($input)/; # try match
  $match = $1;          # assign here because of local scope?
};
if ($@ ne '') {
  # error because invalid reg exp sent
}
else {
  if ($match) {
    # regexp matched
  }
  else {
    # reg exp not matched
  }
}