$ perl -le'
my $string = q/423RY75Y69827EC67592C78657N965R345U299M/;

print $string;

$string =~ s/(([A-MO-Z])[\dN]+\2)/_$1_/ig;

print $string;

substr( $string, 1 + rindex $string, q/_/ ) =~ s/(?<=[^\dN\3])([\dN]+[
+A-MO-Z])/_$1/ig;

print $string;
'
423RY75Y69827EC67592C78657N965R345U299M
423R_Y75Y_69827E_C67592C_78657N965R345U299M
423R_Y75Y_69827E_C67592C_78657N965R_345U_299M

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In reply to Re: match if last char and first char are different excluding certain chars by jwkrahn
in thread match if last char and first char are different excluding certain chars by leocharre

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