RegEx/GetMarkupTag.regex.ps1

<#
.Synopsis
    Gets markup tags
.Description
    Gets one or more specific markup tags. By default, anchor tags.
#>

param(
[Parameter(ValueFromRemainingArguments=$true)]
[string[]]$Tag = @('a')
)


@"
\< # The tag Start
(?<TagName>$($Tag -join '|')) # The name of the Tag is any non number of non-word characters
(?<TagAttributes> # It's attributes are
    .+? # anything until
    (?= # the close of the tag.
        (?> # The close of the tag can be either (IsClosed)/> or (IsOpen)>
            (?<IsClosed>/>)|(?<IsOpen>>)
        )
    )
)
(?(IsOpen)(?: # If the tag was open
        > # match the end tag (so that it's not captured as TagContent)
        (?<TagContent> # then capture the tag content
                (?>
                    (.|\s)+?(?!<\k<TagName>)|
                    (?=\<\k<TagName>)(?<TagDepth>)|
                    (?=\<\/\k<TagName>)(?<-TagDepth>)
                )*(?(TagDepth)(?!))
                                # It is anything until
        )(?=\<\/\k<TagName>) # the closing tag
        (?:\<\/\k<TagName>>)
    )
)
"@