Don't use substitution here: 
$string="garbage validcommand 1234  221 garbage 999 213 validcommand 1
+2 34 garbage";
while ($string =~ /validcommand\s+((\d+\s+)+)/g) {
    push @args, split /\s+/, $1;
}

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In reply to Re: Parsing arguments with surrounding garbage. by busunsl
in thread Parsing arguments with surrounding garbage. by kschwab

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