Regular Expressions 101

Explanation
Pro

Positive Lookbehind(?<=[\s\w])

Character Class[\s\w]

\sany whitespace character

\wany word character

Non-Capturing Group(?:\.{1,2}|\.{4,})

1st Alternative\.{1,2}

\.{1,2}the literal . (46₁₀ / 56₈ / 2E₁₆) , repeated between 1 and 2 times

2nd Alternative\.{4,}

\.{4,}the literal . (46₁₀ / 56₈ / 2E₁₆) , repeated at least 4 times

Positive Lookahead(?=[\s\w])

Character Class[\s\w]

\sany whitespace character

\wany word character

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

26 tokens

(?<=[\s\w])(?:\.{1,2}|\.{4,})(?=[\s\w])

New

I was sent... to protect you.
I was sent.. to protect you.
I was sent.... to protect you.
I was sent ... to protect you.

I was sent... to protect you.
I was sent.. to protect you.
I was sent.... to protect you.
I was sent ... to protect you.