sift: Filter a character vector
In halpo/short: A collection of shortcuts and time savers

sift filters the list to elements matching the pattern. sieve filters them out.

sift(x, pattern, value = TRUE, perl = TRUE, ignore.case = TRUE,
  on.names = FALSE, invert = FALSE, ...)

sieve(..., invert = TRUE)

`x`	a character vector where matches are sought, or an object which can be coerced by `as.character` to a character vector. Long vectors are supported.
`pattern`	character string containing a regular expression (or character string for `fixed = TRUE`) to be matched in the given character vector. Coerced by `as.character` to a character string if possible. If a character vector of length 2 or more is supplied, the first element is used with a warning. Missing values are allowed except for `regexpr` and `gregexpr`.
`value`	if `FALSE`, a vector containing the (`integer`) indices of the matches determined by `grep` is returned, and if `TRUE`, a vector containing the matching elements themselves is returned.
`perl`	logical. Should Perl-compatible regexps be used?
`ignore.case`	if `FALSE`, the pattern matching is case sensitive and if `TRUE`, case is ignored during matching.
`on.names`	Perform filtering on the names of the vector instead.
`invert`	logical. If `TRUE` return indices or values for elements that do not match.
`...`	Passed on