You need to use a back reference. 
$after =~ s#^(\w+)/\1#$1#;

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Tidying up the syntax and changing the test for the bit in between the repeats gives: 

$after =~ s/(\w+)\W+\1/$1/;

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I assumed that there is no need to anchor the pattern to the start of the string so I removed the ^

In reply to Re: using an RE to consolidate repeated words by inman
in thread using an RE to consolidate repeated words by jaa

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