If you need to work with a specific known line number and have a known record width, perhaps you should consider using seek to control your input rather than reading in the entire file. This could also be used to estimate a start position to avoid a fair bit of reading time. Otherwise, a sample of your input file might be helpful (or is that the hash you provided? - if so, do you have the option of changing your input format?).

Update: Upon further consideration, did you not mean a given line number by "specific line"? Is "bakjob1_details" a unique identifier? Does every record header (and only record headers) end with "_details"? It seems like this should all be done in a database, but assuming that the answer to all the above is yes, the following should function:

use strict;
use warnings;

my $filename = 'input.txt';
my %record = ();

#Read records
{
    open FILEHANDLE, "<$filename";
    my @tree_refs = ();
    while (<FILEHANDLE>) {
        if (@tree_refs and /(.*)\_details/) {
            die "Corrupt record encountered at $_";
        } 
        if (/(\S*)\_details/) {
            if ($1) {
                unshift @tree_refs, {};
                $record{$1} = $tree_refs[0];
            } else {
                die "Record without name encountered at $_";
            }
        } elsif (/\=.*\{/) {
            my $name = (split '=')[0];
            $name =~ s/\s*//g;
            unshift @tree_refs, $tree_refs[0]->{$name} = {};
        } elsif (/\}/) {
            shift @tree_refs;
        } elsif (/\=/) {
            (my $name, my $value) = (split '=')[0 .. 1];
            $name =~ s/\s*//g;
            $value =~ s/\s*||\,//g;
            $tree_refs[0]->{$name} = $value;
        } else {
            die "Unexpected condition at $_"
        }
    }
    close FILEHANDLE;
}

#Edit appropriate records
$record{bakjob1}->{debit}->{customer2} = '21.0';
$record{bakjob1}->{credit}->{customer2} = '42.0';
$record{bakjob2}->{debit}->{customer2} = '84.0';
$record{bakjob2}->{credit}->{customer2} = '168.0';

#Output records
open FILEHANDLE, ">$filename";
for my $root_key (keys %record) {
    print FILEHANDLE "  $root_key\_details \= \{\n";
    my @queue = ();
    my $last_depth = 1;

    # Root-level elements
    for my $key (keys %{$record{$root_key}}) {
        if (ref $record{$root_key}->{$key}) { # Stick it on the queue
            push @queue, {record => $record{$root_key}->{$key},
                          key => $key,
                          depth => 2,
                          };
        } else { # Output values
            my $value = $record{$root_key}->{$key};
            print FILEHANDLE ' 'x4 . "$key \= $value\,\n";
        }
    }
    
    while (my $element = shift @queue) {
        if ($last_depth >= $element->{depth}) {
            for (reverse $element->{depth} .. $last_depth) {
                print FILEHANDLE '  'x$_ . "\}\,\n";
            }
        }
        print FILEHANDLE '  'x$element->{depth} . "$element->{key} \= 
+\{\n";
        for my $key (keys %{$element->{record}}) {
            if (ref $element->{record}->{$key}) { # Stick it on the qu
+eue
                push @queue, {record => $element->{$key},
                              key => $key,
                              depth => 1+$element->{depth},
                              };
            } else { # Output values
                my $value = $element->{record}->{$key};
                print FILEHANDLE '  'x($element->{depth}+1) . "$key \=
+ $value\,\n";
            }
        }
        $last_depth = $element->{depth};
    }

    for (reverse 1 .. $last_depth) {
        print FILEHANDLE '  'x$_ . "\}\,\n";
    }
}
close FILEHANDLE;

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In reply to Re: Pattern Matching - a Tricky one by kennethk
in thread Pattern Matching - a Tricky one by John007

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