in reply to Re^5: Regex help
in thread Regex help

Oh, I was vaguely aware of it. But I didn't realize that that was the exact point japhy addressed!

@rt = (
    q/\b/,    # standard word boundary
    q/(?:(?=\w)(?<!\w)|(?=\W)(?<!\W))/,    # [japhy]-explicit-left
    q/(?:(?<=\w)(?!\w)|(?<=\W)(?!\W))/,    # [japhy]-explicit-right
    q/(?(?=\w)(?<!\w)|(?<!\W))/,    # [japhy]-conditional-left
    q/(?(?<=\w)(?!\w)|(?!\W))/,    # [japhy]-conditional-right
    q/(?:(?=\w)(?<!\w)|(?!\w)(?<=\w))/,    # [ysth]-\b-emulation
);
for my $text ('this,', ',that') {
    for my $rxstr (@rt) {
        my $try = $rxstr . (' ' x (31 - length $rxstr));
        my $rx = qr/$rxstr/;
        (my $txt = $text) =~ s/$rx/*/g;
        print "[$try]$txt\n";
    }
}

[download]

[\b                             ]*this*,
[(?:(?=\w)(?<!\w)|(?=\W)(?<!\W))]*this*,
[(?:(?<=\w)(?!\w)|(?<=\W)(?!\W))]this*,*
[(?(?=\w)(?<!\w)|(?<!\W))       ]*this*,
[(?(?<=\w)(?!\w)|(?!\W))        ]*this*,*
[(?:(?=\w)(?<!\w)|(?!\w)(?<=\w))]*this*,
[\b                             ],*that*
[(?:(?=\w)(?<!\w)|(?=\W)(?<!\W))]*,*that
[(?:(?<=\w)(?!\w)|(?<=\W)(?!\W))],*that*
[(?(?=\w)(?<!\w)|(?<!\W))       ]*,*that*
[(?(?<=\w)(?!\w)|(?!\W))        ],*that*
[(?:(?=\w)(?<!\w)|(?!\w)(?<=\w))],*that*

[download]

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