Check if input can be constructed from chemical element symbols. (For a puzzle).

elementary.pl

use strict;
use warnings;

use Data::Dumper;

die "Malfunction. Need input." unless $ARGV[0];

my @e = ( 'H','He','Li','Be','B','C','N','O','F','Ne','Na','Mg','Al','Si','P','S','Cl','Ar','K','Ca','Sc','Ti','V','Cr','Mn','Fe','Co','Ni','Cu','Zn','Ga','Ge','As','Se','Br','Kr','Rb','Sr','Y','Zr','Nb','Mo','Tc','Ru','Rh','Pd','Ag','Cd','In','Sn','Sb','Te','I','Xe','Cs','Ba','La','Ce','Pr','Nd','Pm','Sm','Eu','Gd','Tb','Dy','Ho','Er','Tm','Yb','Lu','Hf','Ta','W','Re','Os','Ir','Pt','Au','Hg','Tl','Pb','Bi','Po','At','Rn','Fr','Ra','Ac','Th','Pa','U','Np','Pu','Am','Cm','Bk','Cf','Es','Fm','Md','No','Lr','Rf','Db','Sg','Bh','Hs','Mt','Ds','Rg','Cn' );

my %eh = map { lc($_) => $_ } @e;

sub solve {
    my ($string) = @_;
    if (length($string) == 0) { return ("."); }

    if ($eh{lc(substr($string, 0, 1))} and my @s = solve(substr($string, 1))) {
        return ( $eh{lc(substr($string, 0, 1))}, @s) ;
    }

    if ($eh{lc(substr($string, 0, 2))} and my @s = solve(substr($string, 2))) {
        return ( $eh{lc(substr($string, 0, 2))}, @s) ;
    }

    return ();
}

if (open(W, $ARGV[0])) {
    while (my $line = <W>) { 
        chomp($line);
    
        #print Dumper solve(join '', split ' ', $line);
        if (solve(join '', split ' ', $line)) { print $line . "\n"; }
    }
    close(W);
} else {
    print( (join "", (solve(join '', split ' ', $ARGV[0]))) . "\n");
}