#!/usr/bin/perl -w

use strict;
use warnings;

my $p_operations = {
    '+' => sub { $_[0] + $_[1] },
    '-' => sub { $_[0] - $_[1] },
    '*' => sub { $_[0] * $_[1] },
    '/' => sub { $_[0] / $_[1] },
};

#  Get operation $op, and values $x and $x in whatever fashion
#  ...

# For testing
my $x  = 12;
my $y  = 7;
my $op = "*";

my $result = $p_operations->{$op}->($x, $y);
print "The result of $x $op $y is:  $result\n";