Remove leading spaces

perl -pE 's/^ +//' src/examples/text_with_spaces.txt

perl -pE 's/^[ \t] +//' src/examples/text_with_spaces.txt

Using \s looks easy but this will also eliminate every row that has only spaces and/or tabs in it.

perl -pE 's/^\s +//' src/examples/text_with_spaces.txt