use strict;
my $str = '[HEADER1]
{
key value
key value
...
[HEADER2]
{
key value
...
}
key value
[HEADER3]
{
key value
[HEADER4]
{
key value
...
}
}
key value
}
';
my $regex = qr/\[(\w*)\]\n/p;
my $subst = '"$1":';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html