Just capture nand2_1 into a variable, like you already did, and then just break it into bits, like so:

my $gate_name = 'nand2_1';
my ($gtype, $gfirst, $gsecond) = ($gate_name =~ /^(\w+)(\d+)_(\d+)/);
print "# $gtype # $gfirst # $gsecond #\n";
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output:

# nand # 2 # 1 #
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