Perl - match begin / end string in a file - perl

Question

How do I write a PERL for the below:
I would like to read in a file.
Then match between GAME and END from the file read in. I want the line that has "GOOD CATCH 1 5 15 5 15" to become "GOOD CATCH 1 10 30 10 30". The final number is multiply by 2 or 3 or 4...etc.
Print out the same file but with the changed above.
Input file
***********
GAME
BALL X1 ;
GOOD CATCH 1 5 15 5 15 ;
END
Output file
***********
GAME
BALL X1 ;
GOOD CATCH 1 10 30 10 30 ;
END
# I am not sure how to match $GOOD CATCH line and multiply the last 4 digit. Is there such a thing as LINDEX or SCAN in perl?
open (infile, "<", "inputfile.txt") or die "could not open:$!";
open (outfile, ">", "outputfile.txt") or die "could not open:$!";
while (<infile>)
if (/GAME/) {
if (/BALL X1/) {
$GOOD CATCH =
}
}
elseif (/END) {
print ;
}
close (inffie);
close (outfile);

Answer 1

I would recommend having a look on a parser like Regexp::Grammars. Anyway, here is a simpler approach using regex:
use strict;
use warnings;
my $fn = "file.txt";
open ( my $fh, '<', $fn ) or die "Could not open file '$fn': $!";
my $str = do { local $/; <$fh> };
close $fh;
$str =~ s/^(GAME.*?^END)/multiply($1)/msge;
print $str;
sub multiply {
my ( $str ) = #_;
$str =~ s/(GOOD CATCH.*?;)/_multiply($1)/ge;
return $str;
}
sub _multiply {
my ( $str ) = #_;
$str =~ s/(\d+)/_mul_number($1)/ge;
return $str;
}
sub _mul_number {
my ($num) = #_;
return $num * 2;
}
Output:
GAME
BALL X1 ;
GOOD CATCH 2 10 30 10 30 ;
END