#!/usr/bin/perl

use strict;
use warnings;

# seltsamer Variablenname
my $var = "Hallo Welt, wie geht es dir?";

# irregulaere Eingabedaten
$_ = "a =5   , $var  = 42, b=3\n";

print m/(?:^|,)\s*\Q$var\E\s*=\s*(\d+)/, "\n";