need a faster version of substr in perl or other suggestion - perl

Question

Does anybody have any ideas on how to speed up this perl code?
I want to keep the way this loop works by eating each match and starting the match again at position zero of the string on the next loop iteration... the reason why i need it this way is because i'm matching language constructs that span multiple lines..
The problem i'm having is that i'm reading a really large file that has thousands of lines of `define... and I think the call to substr is slowing it down... Looking for alternative ways of doing this that are much faster..
#!/bin/perl
$vlog = "out/tb_asc.sv";
open(my $F, "$vlog") || die("cannot open file: $vlog\n");
#lines = <$F>;
for(my $i=0; $i < #lines; $i++) {chomp($lines[$i])};
$bigline = join("\n", #lines);
close($F);
$movingline = $bigline;
sub nextline($) {
#c = split(/\n/, $moving);
$c = $c[0];
chomp($c);
return $c;
}
print ">> << START\n";
$moving = $bigline;
$moving =~ s|//.*$||mg;
$moving =~ s|\s+$||mg;
while(1) {
# Blank Linke
if ($moving =~ /\A$/m) {
# print ">> blank\n";
$moving = substr $moving, $+[0]+1;
next;
}
# timescale
if ($moving =~ /\A\s*`timescale\s+\w+\s*\/\s*\w+$/m) {
print ">> timescale\n";
$moving = substr $moving, $+[0];
next;
}
if ($moving =~ /\A\s*`define\s+(\w+)\s+(.*)$/m) {
$def = $1;
$val = $2;
print "define: $def $val\n";
$moving = substr $moving, $+[0];
next;
}
if ($moving =~ /\A\s*`ifndef\s+(\w+)$/m) {
$def = $1;
$val = $2;
print "ifndef $def\n";
$moving = substr $moving, $+[0];
next;
}
if ($moving =~ /\A\s*`ifdef\s+(\w+)$/m) {
$def = $1;
$val = $2;
print "ifdef $def\n";
$moving = substr $moving, $+[0];
next;
}
if ($moving =~ /\A\s*`else$/m) {
$def = $1;
$val = $2;
print "else\n";
$moving = substr $moving, $+[0];
next;
}
$c = nextline($moving);
print "\n=> processing:[$c]\n";
die("parse error\n");
}