A fuzzy approach...

Advantage: may handle large files (no slurping). 'Regexp's have to handle a single line only.
Disadvantage: bakjob*_details, credit/debit, customer2 have to appear on distinct lines (fragile, relies on proper input). 

use strict;

my %replacement = ("bakjob1_details.debit"  =>  123.45,
                   "bakjob2_details.credit" => -543.21
                  );

sub new_value {
  my ($key, $value) = @_;
  if (defined $replacement{$key}) {
    $value  = $replacement{$key};
  } else {
    warn "WARNING:  '$key' unmodified ($value)\n";
  }
  return $value;
}

my ($bjob, $payment);

while ( <DATA> ) {
  $bjob    = $1, next if /\b(bakjob[12]_details)\b/;
  $payment = $1, next if /\b(credit|debit)\b/;
  # next unless /\bcustomer2\b/; #speed-up?
  s{^
      (\s* customer2 \s* = \s*)
      (\S+?)
      (\s*?,?\s*)
    $
   }
   {
      $1 . new_value("$bjob.$payment",$2) . $3
   }ex;
} continue {
  print;
}

__DATA__
  bakjob1_details = {
    credit = {
      customer1= 2000.0,
      customer2 = -1500.0
# comma missing?
      customer3 = 0.0,
    },
    debit = {
      customer1= 50000.0,
      customer2 = -2000.0,
      customer3 = 0.0,
    }
  },
  bakjob2_details = {
    credit = {
      customer1= 1000.0,
      customer2 = 200.0,
      customer3 = 500.0,
    },
    debit = {
      customer1= 600.0,
      customer2 = 659.0,
      customer3 = 887.0,
    }
  }

[download]

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

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.