You can avoid having to add the newline by using the -l CLO which simplifies things. Which if your array isn't too big makes it

perl  -le"@a = <*.pl>; print for grep{ /\d{6}\./ } @a"
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If your array might be very large, then flattening it to a list doubles your memory consumption, and takes extra time. If that's a danger, then using

perl  -le" @a = <*.pl>; /\d{6}\./ and print for @a"
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avoids those problems.