Titlecase.regex

smallWordExpression = {
    (?<!q&)a|an|and|as|at(?!&t)|but|by|en|for|if|in|of|on|or|the|to|v[.]?|via|vs[.]? 
}

apostropheExpression = {
    (?: ['’] [[:lower:]]* )?
}

titlecaseExpression = {
    \b (_*) (?:
        (
			# File path
			(?<=[\ ][/\\]) [[:alpha:]]+ [-_[:alpha:]/\\]+
        	# or URL, domain, or email
          	| [-_[:alpha:]]+ [@.:] [-_[:alpha:]@.:/]+ $apostropheExpression
		)
        # or small word (case-insensitive)
        | ( (?i: $smallWordExpression ) $apostropheExpression )
        # or word w/o internal caps
        | ( [[:alpha:]] [[:lower:]'’()\[\]{}]* $apostropheExpression )
        # or some other word
        | ( [[:alpha:]] [[:alpha:]'’()\[\]{}]* $apostropheExpression )
    ) (_*) \b
}

# Exceptions for small words

## Capitalize at start of title
startExceptionExpression = {
	(?i)
    # Start of title
    (  \A [[:punct:]]*
    # or of subsentence
    |  [:.;?!][\ ]+
    # or of inserted subphrase
    |  [\ ]['"“‘(\[][\ ]*     )
    # followed by small word
    ( $smallWordExpression ) \b
}

## Capitalize at end of title
endExceptionExpression = {
    (?i)
    # Small word
    \b ( $smallWordExpression )
    # at the end of the title
    (?= [[:punct:]]* \Z
    # or of an inserted subphrase?
    |   ['"’”)\]] [\ ] )
}

# Exceptions for small words in hyphenated compound words

## "in-flight" -> In-Flight
startHyphenatedCompoundExpression = {
    (?i)
    \b
    # Negative lookbehind for a hyphen; we don't want to match man-in-the-middle but do want (in-flight)
    (?<! -)
    ( $smallWordExpression )
    # Lookahead for "-someword"
    (?= -[[:alpha:]]+)
}

## "Stand-in" -> "Stand-In" (Stand is already capped at this point)
endHyphenatedCompoundExpression = {
    (?i)
    \b
    # Negative lookbehind for a hyphen; we don't want to match man-in-the-middle but do want (stand-in)
    (?<!…)
    # $1 = first word and hyphen, should already be properly capped
    ( [[:alpha:]]+- )
    ( $smallWordExpression )
    # Negative lookahead for another '-'
    (?!	- )
}