Sure, just remove the newline:

$basename =~ s/\S*RDL/RDL/; $basename =~ s/.ruv$//;
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Or

s/\S*RDL/RDL/, s/.ruv$// for $basename;
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Or

$basename =~ s/\S*RDL((?s:.*)).ruv$/RDL$1/;
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but why would you? The two lines are easy to understand, and certainly more efficient that the latter single substitution.