Regular Expressions 101

Explanation
Pro

1st Alternative^([^a-zA-Z]*)([a-z])

^start of line

Group 1([^a-zA-Z]*)

Negated Character Class[^a-zA-Z]*

*matches any number of characters outside the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Group 2([a-z])

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

2nd Alternative(\.\s*)([a-z])

Group 3(\.\s*)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\s*any whitespace character, repeated any number of times

Group 4([a-z])

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

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.

25 tokens

^([^a-zA-Z]*)([a-z])|(\.\s*)([a-z])

New

.this sentence
and this
This is already
.this sentence
and this.also this. and this.This one is not.

.this sentence
and this
This is already
.this sentence
and this.also this. and this.This one is not.