use strict;
my $str = 'name=toto
tat\\=a
bla\\bla=tor
blood\\\\=orange
wrong\\\\\\=cops
right\\\\\\\\=escaping
extrem\\\\\\\\\\=slash
hoho\\\\\\\\\\\\=ho
is\\\\\\\\\\\\\\=magic
noend=
dou=bl=equal
ma\\=tche!=operation
is\\\\!=not
is<=inferior
is>=superior
tha>t=isno<t
-----
^(.+)((?<!\\\\)=)(.+)$';
my $regex = qr/^(.+)(?<!\\)((?:\\\\)*)(\!\=|(?<!\!|\<|\>)=|\<\=|\>\=)(.+)$/mp;
my $subst = '[$1$2] $3 [$4]';
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