Dado que a pergunta é pedir um regex especificamente:
grep -Eo '\s(\w+).$' file
UAT01
Test04
Dev02
Test0
Explicação:
'\s' matches any whitespace character.
'(\w+)' is the first Capturing Group
'\w+' matches any word character and it is equal to [a-zA-Z0-9_]
'+ ' Quantifier — Matches between one and unlimited times, as many times as possible.
'.' matches any character (except for line terminators)
'$' asserts position at the end of the string, or before the line terminator right at the end of the string.
As últimas strings podem ser extraídas com muito mais facilidade usando cut
ou awk
cut -d' ' -f 7 file
awk '{print $7}' file