# From what Anonymous monk writes, it seems the task is:
# replace a field (in double quotes) of a comma
# separated record in a file called guidpair.txt with
# something else.
# He gives me the line, the text of the last field, and
# the replacement text which he somehow gets from another
# file.
# The line
# "Web","rad","INPUT","onclick","746B97B8-486A-094F-9426292F0C0BB644 F",""
# should be
# "Web","rad","INPUT","onclick","5C1DAEF0-9386-44a5-B92A-31FE2C79236A",""
#
# Given that information, the program could look like this:

my $infile = 'guidpair.txt';
my $tempfile = "$infile.new";

# ===================================================
# CAVEAT: if $infile.new exists, it will be clobbered
# XXX Better use File::Temp here?
# ===================================================

open(I,"<$infile") or die "Can't open $infile: $!\n";
open(O,">tempfile") or die "Can't write $tempfile: $!\n";

while(<I>) {
    if (/"Web","rad","INPUT","onclick","746B97B8-486A-094F-9426292F0C0BB644 F",""/) {
        s/746B97B8-486A-094F-9426292F0C0BB644 F/5C1DAEF0-9386-44a5-B92A-31FE2C79236A/;
    }
    print O;
}
close(I) or die "Can't close input file $infile: $!\n";
close(O) or die "Can't close temp file $tempfile: $!\n";
rename($tempfile,$infile)
    or die "Can't rename $tempfile to $infile: $!\n";
__END__