See perlre. [] is a character class (perlrecharclass):

c:\>perl -le "print $_, qq(\t), /\.[docx|pdf]$/ ||0 for qw(.pdf .docx 
+.p .d .f .d .o .c .x .|);"
.pdf    0
.docx   0
.p      1
.d      1
.f      1
.d      1
.o      1
.c      1
.x      1
.|      1

[download]

(?:) is a non-capturing group:

c:\>perl -le "print $_, qq(\t), /\.(?:docx|pdf)$/ ||0 for qw(.pdf .doc
+x .p .d .f .d .o .c .x .|);"
.pdf    1
.docx   1
.p      0
.d      0
.f      0
.d      0
.o      0
.c      0
.x      0
.|      0

[download]

edit: fix typo (missing "?:" in my second one-liner)

In reply to Re: Grep match alternative by pryrt
in thread Grep match alternative by IB2017

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.