Dear all,

I'm tackling a problem for which I could manually hard-code the result, but I'm very aware that I can achieve the same results with a regexp string, which would be more useful...

I have a list of chemical formulas, a sample of which is listed below, I simply want to extract, for each formula, the elements within.

This is what I've got for my one_liner: 
 perl -ne 'chomp;split /\s+/,$_;print $_[1],"\n";while($_[1] =~ /([A-Z
+][a-z]?(\d*))/g){print "\t",$1,"\t",$2,"\n";}'

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My question is, is this the only way I could get through the variable number of groups? I feel like I could write it into the regular expression itself, that the variable number of groups get directly inserted into an array or a hash, and I can exclude the while loop...is this possible?

Another question would be, if there is only one atom of an element, then there wouldn't be any output for the second group, but can I convert that empty output into a zero string, "inline"?

Thanks
Sam 
__DATA__
CH4N2O
C9H12N2O6
C5H11NO2
C5H4N4O2
C10H11N4O9P
C10H12N4O6
C5H10O5
C5H12O5
C5H10O5
C27H44O
C1694H2993O101

[download]

In reply to Recursive capture of a variable number of elements using regexp by seaver

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