Regular Expressions 101

Pro

Positive Lookbehind(?<=\d)

\da Unicode decimal digit

\s+a Unicode whitespace character, repeated at least once

Positive Lookahead(?=[A-Z])

Character Class[A-Z]

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

(?<=\d)\s+(?=[A-Z])

New

'Reservoir 1 Compartment 1', 
'Reservoir 1 Common Inlet', 
'Reservoir 2 Compartment 1',
'Vyrnwy Line 2 Balancing Tank 1' 
'Reservoir 1'