my $output; 
       while( my $line = <DATA> ) {
           # get rid of line terminator:
           chomp $line;
           # Get rid of line numbers:
           $line =~ s/^N[0-9]{2}\ //;
           # Replace * and the beginning of the line with !:
           $line =~ s/^\*(.*)/!$1/ and print $line and next if $line;
           # Keep any numbers prefixed with X,Y or Z.:
           $line =~ s/(X|Y|Z)([0-9.-]+)/ $2/g if $line;
           # Throw the rest away:
           $line =~ s/[A-Z][0-9.+-]+//g if $line;
           open 
           print $line;
       }
       __DATA__
O1407!SILH 5B NECK PROFILE STD.>
N1! 11-14-01
N2!T1 3/4" ENDMILL
N3! OUTPUT IN ABSOLUTE
N4L0200
N5! SUB NUMBER: 2
N6G90G0X11.108Y-18.25
N7G1Z-1.13F80.

##</code><code>##

$file = "file.txt";
open (FILE, "$file");
       my $output; 
       while( my $line = <FILE> )... etc.