# Matches Liquid Expressions
\{{2,2}                                  # {{ opens a expression 
\s{0,}                                   # Optional opening whitespace
# The Liquid Expression is anything until the expression close, which is
(?<Expression>(?:.|\s){0,}?(?=\z|\s{0,}  # Optional closing whitespace
\}{2,2}                                  # Followed by a }}
))\s{0,}                                 # Now we match the close: First Optional whitespace
\}{2,2}                                  # Followed by }}

