I tried doing that, but I failed.

What did you try? How did it fail?

Hard to tell, but is all you are looking for this?

my $formula = 'C6H5OH';
$formula =~ s/H\d//g;
print "$formula\n";

[download]

Update: As runrig suggests below the more general s/H\d*//g; may be more appropriate to your needs.

In reply to Re: How to avoid an alphabet and integer next to it in a string? by hippo
in thread How to avoid an alphabet and integer next to it in a string? by piscean

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