my $data         = 'Just another Perl hacker,';
my $expression   = 's/(another)/a/; print "Hello world!\n";';

my $match_var;
my $result = eval <<"END_EVAL";
  my \$success = \$data =~ $expression;
  \$match_var = \$success ? \$1 : undef;
  \$success;
END_EVAL

if( $result ) {
    print "$match_var => $data\n";
}