Well, if you have N335G03X247.7.16Y580.07K and your pattern is N<n>G03X<x>Y Then we know that numbers are actual numbers 0-9 and can contain a dot as decimal separator, thus the regular expression to match this is:

use strict;
use warnings;
my $line = "N335G03X247.16Y580.07K6.89J96.62H1M25 N340M20 N345G45";
my($n, $x);
if($line =~ /N([0-9\.]+)/){ $n = $1 };
if($line =~ /G03X([0-9\.]+)/){ $x = $1 };
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You can then use this to get the rest of the variables, then check if they have the right values... or at least defined, for example if $n and $x has been defined:
if($n && $x){ print "n=$n and x=$x \n" }
You can exchange 0-9 with \d, as in:

if( $line =~ /N([\d\.]+)/ ){ $n = $1 };
if( $line =~ /G03X([\d\.]+)/ ){ $x = $1 };
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